Pre 1883 history

There were three volcanic cones on Krakatoa island:

Rakata: (820 m or 2,690 ft) to the south;

Danan: (450 m or 1,480 ft) near the center

Perboewatan: (120 m or 390 ft) to the north.

Pre-1883 history

At some point in prehistory, an earlier caldera-forming eruption had occurred, leaving as remnants Verlaten (or Sertung); Lang (also known as Rakata Kecil, or Panjang); Poolsche Hoed ("Polish Hat"); and the base of Rakata. Later, at least two more cones (Perboewatan and Danan) formed and eventually joined with Rakata, forming the main island of Krakatoa. At the time of the 1883 eruption, the Krakatoa group comprised Lang, Verlaten, and Krakatoa itself, an island 9 km (5.6 mi) long by 5 km (3.1 mi) wide. There were also the tree-covered islet near Lang (Poolsche Hoed) and several small rocky islets or banks between Krakatoa and Verlaten.

There were three volcanic cones on Krakatoa island: Rakata, (820 m or 2,690 ft) to the south; Danan, (450 m or 1,480 ft) near the center; and Perboewatan, (120 m or 390 ft) to the north.

416 AD event

The Javanese Book of Kings (Pustaka Raja) records that in the year 338 Saka (416 AD): A thundering sound was heard from the mountain Batuwara [now called Pulosari, an extinct volcano in Bantam, the nearest to the Sunda Strait] which was answered by a similar noise from Kapi, lying westward of the modern Bantam [(Banten) is the westernmost province in Java, so this seems to indicate that Krakatoa is meant]. A great glowing fire, which reached the sky, came out of the last-named mountain; the whole world was greatly shaken and violent thundering, accompanied by heavy rain and storms took place, but not only did not this heavy rain extinguish the eruption of the fire of the mountain Kapi, but augmented the fire; the noise was fearful, at last the mountain Kapi with a tremendous roar burst into pieces and sank into the deepest of the earth. The water of the sea rose and inundated the land, the country to the east of the mountain Batuwara, to the mountain Rajabasa [the most southerly volcano in Sumatra], was inundated by the sea; the inhabitants of the northern part of the Sunda country to the mountain Rajabasa were drowned and swept away with all property... The water subsided but the land on which Kapi stood became sea, and Java and Sumatra were divided into two parts.

There is no geological evidence of a Krakatoa eruption of this size around that time; it may describe loss of land which previously joined Java to Sumatra across what is now the narrow east end of the Sunda Strait; or it may be a mistaken date, referring to a later eruption in 535 AD, for which there is some corroborating historical evidence.

535 AD event

David Keys, Ken Wohletz, and others have postulated that a violent volcanic eruption, possibly of Krakatoa, in 535 may have been responsible for the global climate changes of 535–536. Keys explores what he believes to be the radical and far-ranging global effects of just such a putative 6th-century eruption in his book Catastrophe: An Investigation into the Origins of the Modern World. But see Extreme weather events of 535–536#Possible explanations for other explanations, including an eruption of Ilopango in El Salvador in Central America.

Thornton mentions that Krakatoa was known as "The Fire Mountain" during Java's Sailendra dynasty, with records of seven eruptive events between the 9th and 16th centuries.These have been tentatively dated as having occurred in 850, 950, 1050, 1150, 1320, and 1530.

1680

In February 1681, Johann Wilhelm Vogel, a Dutch mining engineer at Salida, Sumatra (near Padang), on his way to Batavia (now Jakarta) passed through the Sunda Strait. In his diary he wrote:

...I saw with amazement that the island of Krakatoa, on my first trip to Sumatra [June 1679] completely green and healthy with trees, lay completely burnt and barren in front of our eyes and that at four locations was throwing up large chunks of fire. And when I asked the ship's Captain when the aforementioned island had erupted, he told me that this had happened in May 1680 ... He showed me a piece of pumice as big as his fist.

Vogel spent several months in Batavia, returning to Sumatra in November 1681. On the same ship were several other Dutch travellers, including Elias Hesse, a writer. Hesse's journal reports:

...on the 19th [of November 1681] we again lifted anchor and proceeded first to the north of us to the island of Sleepzie (Sebesi), uninhabited, ... and then still north of the island of Krakatou, which erupted about a year ago and also is uninhabited. The rising smoke column of this island can be seen from miles away; we were with our ship very close to shore and we could see the trees sticking out high on the mountain, and which looked completely burned, but we could not see the fire itself.

The eruption was also reported by a Bengali sea captain, who wrote of the event later, but had not recorded it at the time in the ship's log. Neither Vogel nor Hesse mention Krakatoa in any real detail in their other passages, and no other travellers at the time mention an eruption or evidence of one. (In November 1681, a pepper crop was being offered for sale by inhabitants.) In 1880 Verbeek investigated a fresh unweathered lava flow at the northern coast of Perboewatan, which could not have been more than two centuries old.

Dutch activity

In 1620 the Dutch set up a naval station on the islands and somewhat later a shipyard was built. Sometime in the late 17th century an attempt was made to establish a pepper plantation on Krakatoa, but the islands were generally ignored by the Dutch East India Company. In 1809 a penal colony was established at an unspecified location, which was in operation for about a decade. By the 1880s the islands were without permanent inhabitants; the nearest settlement was the nearby island of Sebesi (about 12 km or 7.5 mi away) with a population of 3,000.

Several surveys and mariners'charts were made, and the islands were little explored or studied. An 1854 map of the islands was used in an English chart, which shows some difference from a Dutch chart made in 1874. In July 1880, Rogier Verbeek made an official survey of the islands, but was only allowed to spend a few hours there. He was able to collect samples from several places, and his investigation later proved important in judging the geological impact of the 1883 eruption